Hyperfine spectroscopic study of Hf2Fe hydrides and their thermal stability

Cluster approach to the Ti2Ni structure type

“…4). The centres of these tetrahedra, which are found to be responsible for the interesting magnetic behaviour of the Hf 2 Fe compound upon hydrogenation (Buschow & VanDeepen, 1979;Vulliet et al, 1984;Soubeyroux et al, 1987;Teisseron et al, 1987;Forker et al, 1999), mimic diamond positions inside the Ti 2 Ni unit cell (Yang, 1988). Using the HyperChem software package (Hypercube, Inc., 1994) we performed ab initio LCAO (linear combination of atomic orbitals) calculations of the neutral and one-electron (positively and negatively) charged Fe and Co tetrahedra with dimensions as experimentally established in the Laves phases [HfFe 2 , Fe-Fe distance is 2.484 Å (Ivanović et al, 2000), HfCo 2 , Co-Co distance is 2.443 Å (Ivanović et al, 2000)], Ti 2 Ni structure-type compounds [Hf 2 Fe, Fe-Fe distance is 2.94 Å (Cekić et al, 1991), Hf 2 Co, (Co-Co distance is 3.044 Å (Cekić et al, 1993(Cekić et al, , 1998] and the intermediate distance (d = 2.7 Å ) between these two.…”

“…Among the most powerful methods for the investigation of the local electronic properties in the solid state are various techniques of hyperfine interaction (HFI) measurements (Heer & Novey, 1959;Kaufmann & Vianden, 1979). Extensive investigations of the Hf 2 TM (TM-transition metal) intermetallic compounds (Vulliet et al, 1984;Cekić et al, 1988;Akselrod et al, 1990;Koički et al, 1993;Ivanović et al, 1999;Forker et al, 1999), of the Ti 2 Ni structure type using the time-differential perturbed angular correlation of -rays (TDPAC) technique, have shown that the intensities of the principle component V zz of the electric field gradient (EFG) at 16(c) and 48(f) crystallographic positions differ by almost an order of magnitude ( Fig. 1).…”

Hydrogen production and storage—Investigation of Hf-based intermetallics

“…The hydriding reaction was carried isothermally; within the temperature range 573-823 K (300-550 • C) for Hf 2 Ni and Hf 2 Co and within the temperature range 348-573 K (75-300 • C) for Hf 2 Fe. Hf 2 Fe was hydrated at lower temperatures because of hydride decomposition at higher temperatures [21].…”

Perturbed angular correlation study of static and dynamic hyperfine interactions at181Tain the Laves-phase hydridesErFe2Eek1, Forker2 2002Phys. Rev. BSelf Cite3010View full textAdd to dashboardCite

“…In particular, PAC spectroscopy has been used to study the hydrogen motion in a number of H absorbing pure metals 2,3 and intermetallic compounds. 4,5 Similar to NMR, PAC spectroscopy allows the observation of the nuclear spin relaxation caused by time-dependent hyperfine interactions ͑HFI's͒, which may provide information on the activation energy and other parameters of a diffusion process. In PAC studies of hydrogen diffusion, the relevant interaction is usually the dynamic quadrupole interaction ͑QI͒ between the quadrupole moment of the PAC nucleus and the fluctuating electric-field gradient ͑EFG͒ caused by the moving H charge.…”

“…One has a lattice parameter (a ϳ7.28 Å) close to that of uncharged ErFe 2 ; the other one corresponds to ErFe 2 H x with xϳ1. 5. The H site occupation has been studied by neutron diffraction of c-ErFe 2 D x .…”